1. Field of the Invention
The present invention relates to a vibrating column pump, and more particularly to a vibrating column pump which pumps liquid by making use of liquid vibration, in a vibrating pipe, generated at the time when the vibrating pipe with a control valve is vibrated in a longitudinal direction thereof.
2. Description of the Prior Art
Conventionally, there has been proposed a vibrating column pump which obtains a pumping action by vibrating a cylindrical straight pipe in a longitudinal direction thereof. This type of the vibrating column pump is disclosed in, for example, Laid-Open patent publication No. 58-144700, Laid-Open patent publication No. 61-275600 and Laid-Open utility model publication No. 61-110900. In this type of vibrating column pump, a lower portion of the vibrating pipe is submerged in the liquid in a tank, and the vibrating pipe is vertically vibrated by a vibrator provided on the outer periphery of the vibrating pipe to thus pump liquid. Therefore, in the case where liquid is pumped by the application of the vibrating column pump, it is necessary to carry out a preliminary arrangement that the vibrating pipe is operably installed in the tank in such a manner that the lower portion of the vibrating pipe is submerged in the liquid.
Since such preliminary arrangement is troublesome, an integral type of vibrating column pump has been proposed in Laid-Open patent publication No. 1-219400. This vibrating column pump comprises a cylindrical weak magnetic material provided on the outer periphery of the vibrating pipe, a plurality of permanent magnets having respective different polarities disposed in a longitudinal direction of the vibrating pipe and magnetized in a radial direction, and a plurality of magnet coils provided outside the permanent magnets and disposed in a longitudinal direction of the vibrating pipe. The vibrating pipe and the permanent magnets jointly constitute a movable unit, the magnet coils constitutes a stationary unit, and the movable unit is reciprocatingly moved in a longitudinal direction of the vibrating pipe by supplying an alternating current to the magnet coils. Further, the movable unit and the stationary unit are housed in a casing, thereby constructing an integral type of pump which can be immediately used only by connecting a suction pipe and an outlet pipe to the casing.
However, in the vibrating column pump disclosed in Laid-Open patent publication No. 1-219400, the liquid contacts both of the movable unit and the stationary unit while pumping the liquid. Therefore, the entire components of the pump must be replaced with new ones when a liquid contacting portion is replaced after use. Accordingly, in case of a living body related liquid such as blood, since the liquid contacting portion must be pasteurized after use, this type of the vibrating column pump cannot be used.
Since sealing is not effected between the movable unit and the stationary unit, the pumped liquid enters into the clearance between the movable unit and the stationary unit. For example, in case of a living body related liquid such as blood or a biotechnology related liquid such as culture solution, the liquid enters into the clearance between the movable unit and the stationary unit, thus cells in the liquid are easily subject to damage. The conventional vibrating column pump is also problematic in that various germs propagate themselves in the clearance between the movable unit and the stationary unit while the pump is not in operation.
Since sealing is not effected between the movable unit and the stationary unit, air passes through the clearance between the movable unit and the stationary unit and flows backward from a valve chamber into the vibrating pipe in the self-priming process, thus self-priming effect cannot be achieved. Further, there exist structural elements such as a spring in the flow passage thus the pumped liquid is contaminated by foreign matter caused by corrosion of the structural elements.